A float glass is formed in a float bath including molten tin. It has flat and smooth surfaces that are formed without grinding and polishing, because the plate shape of a float glass is not given by a process in which molten glass is forced to be flattened by rolls, but by a process in which molten glass freely spreads over molten tin due to the difference of their specific gravities. Not a few kinds of float glasses with functional films on their surfaces have come to be generally used. For example, a contamination-resistant float glass is used for buildings, automobiles, cooking apparatus and the like. Such a contamination-resistant float glass can be produced by making a solution including a silane-based compound contact with a surface of a float glass. During the process, the silane-based compound is adsorbed by reacting with a hydroxyl group on the surface. Japanese Unexamined Patent Publication No. 70917/1989 discloses such a process. In this process, a glass plate dipped into a solution including a silane-based compound is removed from the solution and dried. The both sides of the glass are covered with films.
Known contamination-resistant glasses produced by a process as described above, however, are uneven in durability, especially in heat-resistance and abrasion-resistance. These characteristics are very important for a contamination-resistant glass used in a cooking apparatus and the like.